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As a result of a tip-off to the Daily Dispatch newspaper, a prominent opposition MP, Dennis Markham, is photographed leaving a call girl's flat. Two hours later, Kleist, Military Attaché to the East German embassy, is photographed leaving the same building. The paper runs the story and Markham is caught up in a political scandal.

Two of the reporters working on the story are the young and ambitious Nick Mullen, whose only interest is in getting a 'good story', and Vernon Bayliss, an old friend of Markham's who is anxious to clear his name. While Bayliss acts on information from an anonymous phone caller known only as 'George', Mullen gets an anonymous tip-off which leads him to a photograph of Markham and Kleist together at an Eastern European Peace Conference.

In spite of Bayliss's protestations that, given time, he can prove Markham's innocence, Mullen files his story, the paper publishes it, Markham resigns, and Mullen's reputation is made. But he now begins to suffer qualms over what he has done. Bayliss claims that he is being followed by the Special Branch, and when Mullen accompanies him back to his flat, they find that the place has been ransacked.

The next day, Mullen learns that Bayliss has died in the night of a heart attack. Enlisting the help of Markham's secretary, Nina Beckman, Mullen learns that just before the scandal broke, Markham was due to ask a question in Parliament about the death of a boy on the run from a detention centre, about which the authorities were strangely uneasy.

Gradually Mullen discovers the truth: the boy strayed on to an American air base and caused a plane with an atomic pay load to crash, almost bringing about a nuclear catastrophe. However, the paper refuses to publish Mullen's exposé, thanks to the defence contract interests of its proprietor, Sir Victor Kingsbrook. Although Mullen and Nina are now themselves under surveillance, they manage to get the story out to the foreign press and a major political scandal erupts. An explosion destroys Mullen's flat, and both he and Nina are killed.